The invention relates to a compact electrohydraulic motor pump unit.
Such a motor pump unit has been disclosed by DE 299 06 881 U1. This unit possesses a housing which forms a reservoir for a pressurized fluid and in which an electric motor is located. A housing mid-section is of tubular form and closed off at one end face by a first housing lid or, in more general terms, by a first housing sealing section. In front of the other end face of the housing mid-section is located a second housing sealing section which, in the conventional motor pump unit, does not however lie directly on the housing mid-section. Between the second housing sealing section and the housing mid-section, instead, is located a support plate on which a radial piston pump, drivable via the motor shaft of the electric motor, and a similarly drivable gear pump are fixed. Located in the support plate are ducts via which pressurized fluid can be conveyed by the pumps to two delivery connections externally on the support plate.
In the conventional motor pump unit, the interior of the housing has to be sealed off peripherally from the outside between the housing mid-section and the first housing sealing section, between the housing mid-section and the support plate and between the support plate and the second housing sealing section. This is disadvantageous, as the risk of a leakage increases with the number of sealing points and with the length of the seals. Today, however, great importance is attached to clean production areas and the protection of the environment.
It is therefore an object of the present invention further to develop such a compact electrohydraulic motor pump unit such that the number of sealing points between individual housing sections is reduced.
This object is achieved, according to the invention, in that, in a compact electrohydraulic motor pump unit of the introductory-mentioned type, the delivery connection is located externally on the second housing sealing section, in that the second housing sealing section and the tubular housing mid-section, sealing the interior of the housing from the outside, rest on one another peripherally, and in that the support plate is located entirely within the housing. In a motor pump unit according to the invention, therefore, the support plate has lost its function as a housing section by comparison with the motor pump unit in accordance with the above-mentioned state of the art. The second housing sealing section lies, like the first housing sealing section, directly on the housing mid-section, so that there are now only two peripheral sealing points of large diameter. The risk of a leakage to the exterior is significantly reduced thereby.
Advantageous embodiments of a compact electro-hydraulic motor pump unit according to the invention are provided.
In an effort to keep down the installation effort required for a motor pump unit according to the invention, a tube is provided which lies in the pressurized flow path from the pump to a delivery connection on the second housing sealing section and is connected axially by a plug-in fitting to the second housing sealing section at one end and connected axially by a plug-in fitting to a counterpart at the other end. This permits particularly simple assembly in the axial direction of the motor shaft of the electric motor. In this case, in principle, axial plugging-in of the tube is also possible if although the ends of the tube point in the axial direction they are not aligned with one another and the tube is bent. Preferably, however, the tube is straight and extends axially. Special working steps for bending the tube are thereby avoided. Preferably, the tube is plugged into a bore at each of its ends. The diameter of the tube may then be smaller than in a case where the ends are fitted onto pegs.
The tube lies in the pressurized flow path of the pressurized fluid, in which pressure pulses occur, as a result of which the tube might perform small axial movements because of the dimensional tolerances arising in the dimensions of the components and on the tube itself. In order to prevent this, and wear associated therewith and the evolution of noise attributable thereto, the invention provides that the tube is pressed against the other section in one axial direction by a spring element, which is tensioned between the tube and one section of the two sections comprising the counterpart and the second housing sealing section. The spring element is advantageously tensioned between an external shoulder of the tube and the counterpart or the second housing sealing section. It is particularly economical of space and cost-effective for the spring element to be formed by an O-ring. In order to obtain a sufficiently large supporting surface for the spring element even when the tube wall thickness is slight, the invention provides for the insertion of a shim between the spring element and the tube.
Compact electrohydraulic motor pump units of substantially the same construction customarily form a complete series with different structural sizes and different specifications. In order to be able to use the same tube with as many versions as possible, the invention provides that a length-compensation disk is threaded onto the turned-down end of a tube. Preferably, the length-compensation disk lies between the O-ring and the external shoulder of the tube, so that it is retained on the tube before and during assembly of the tube by the O-ring, which is pushed onto the tube with tension.
Depending upon the side of the support plate on which a pump is disposed, and depending on what kind of pump is involved, a tube extends, between the support plate and the second housing sealing section, or, between a connecting flange of the pump and the second housing sealing section. The latter will be the case, for example, if a gear pump or vane-cell pump is disposed on the side of the support plate remote from the electric motor and comprises a radially descending delivery outlet. The former will be the case, primarily, if the pump is seated on the side of the support plate facing toward the electric motor.
It is be desirable to be able to use compact electrohydraulic motor pump units flexibly, with one pump or with two pumps which can convey in different hydraulic circuits, and adjusted to the spatial conditions at a machine tool for which such units are primarily used. Therefore, the second housing sealing section is provided with two delivery connections and two plug-in connections for a tube. If two pumps are driven by the electric motor, one can pump to one delivery connection and the other to the other delivery connection. In this case, the form of the pressurized flow paths is such that either one pump or, only because of different installation, the other pump pumps to one delivery connection. Similarly, the sections may be so assembled that, where only one pump is present, either one delivery connection or the other delivery connection is used. In particular, the support plate has two plug-in connections for a tube, a tube extending between one plug-in connection of the support plate and one plug-in connection of the second housing sealing section and other plug-in connection of the support plate being closed off. In this case, therefore, a pump in whose pressurized flow path ducts also lie within the support plate can pump, by selection of the appropriate plug-in connection on the support plate, to one delivery connection or to the other. Installation of the support plate in different angular attitudes relative to the axis of the motor shaft would, admittedly, permit pumping to one delivery connection or to the other delivery connection even with only one plug-in connection in the support plate and two plug-in connections in the second housing sealing section. In that case, however, the two plug-in connections in the housing sealing section would have to be located at the same distance from the axis of the motor shaft. This again is not in all cases compatible with the arrangement of the plug-in connections in the second housing sealing section that is necessary for the use of two pumps.
Special embodiments with two pumps are also provided by the invention.